Tech Briefs

Instrumented Spindle Improves Manufacturing of Optical Materials

Sensors and data acquisition system provide real-time visibility of grinding system operation. Lion Precision and Professional Instruments, St. Paul, Minnesota High-performance materials such as ceramics, optics, and alloy steels are manufactured using abrasive grinding technology. Until now, the grinding wheel and process conditions have been difficult to measure in production.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Optics, Manufacturing equipment and machinery, Turning

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Flexible Laser Design Targets Low-Volume Material Processing Needs

A flexible approach to diode-pumped laser design combines customized performance with cost-effective manufacturing. Coherent, Inc., Santa Clara, California Q-switched, diode-pumped solid-state lasers with an end-pumped cavity design are now widely used in micromachining, materials processing, marking, and related applications. They are used to process a broad range of materials including metals, glass, plastics, and semiconductors. But this application diversity creates a concomitant need for laser diversity. Namely, while each application requires superior reliability and performance, the definition of “superior performance” is very application-specific. For example, some metal ablation applications may benefit from a long laser pulse, whereas semiconductor scribing needs a short pulse and a very high pulse repetition rate.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Lasers, Product development, Forming

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Aligning Optical Fibers by Means of Actuated MEMS Wedges

Wedges would be fabricated using gray-scale exposure of photoresist. Goddard Space Flight Center, Greenbelt, Maryland Microelectromechanical systems (MEMS) of a proposed type would be designed and fabricated to effect lateral and vertical alignment of optical fibers with respect to optical, electro-optical, optoelectronic, and/or photonic devices on integrated circuit chips and similar monolithic device structures. A MEMS device of this type would consist of a pair of oppositely sloped alignment wedges attached to linear actuators that would translate the wedges in the plane of a substrate, causing an optical fiber in contact with the sloping wedge surfaces to undergo various displacements parallel and perpendicular to the plane. In making it possible to accurately align optical fibers individually during the packaging stages of fabrication of the affected devices, this MEMS device would also make it possible to relax tolerances in other stages of fabrication, thereby potentially reducing costs and increasing yields.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Fiber optics, Integrated circuits, Microelectromechanical devices, Sensors and actuators, Fabrication

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Optical Characterization of Molecular Contaminant Films

A theoretical model is correlated with measured spectral transmittances and VUV exposures of spacecraft optics. Lyndon B. Johnson Space Center, Houston, Texas A semi-empirical method of optical characterization of thin contaminant films on surfaces of optical components has been conceived. The method was originally intended for application to films that become photochemically deposited on such optical components as science windows, lenses, prisms, thin-film radiators, and glass solar-cell covers aboard spacecraft and satellites in orbit. The method should also be applicable, with suitable modifications, to thin optical films (whether deposited deliberately or formed as contaminants) on optical components used on Earth in the computer microchip laser communications and thin-film industries.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Optics, Coatings, colorants, and finishes, Glass, Satellites, Spacecraft

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Coating MCPs With AlN and GaN

Emission of electrons is increased.A development effort underway at the time of reporting the information for this article is devoted to increasing the sensitivity of microchannel plates (MCPs) as detectors of photons and ions by coating the MCPs with nitrides of elements in period III of the periodic table. Conventional MCPs are relatively insensitive to slowly moving, large-mass ions — for example, ions of biomolecules under analysis in mass spectrometers. The idea underlying this development is to coat an MCP to reduce its work function (decrease its electron affinity) in order to increase both (1) the emission of electrons in response to impingement of low-energy, large-mass ions and (2) the multiplying effect of secondary electron emission.

Posted in: Briefs, Electronics & Computers, Product development, Coatings, colorants, and finishes, Reliability

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Automatic Locking of Laser Frequency to an Absorption Peak

Initial manual tuning is ordinarily not necessary. An electronic system adjusts the frequency of a tunable laser, eventually locking the frequency to a peak in the optical absorption spectrum of a gas (or of a Fabry-Perot cavity that has an absorption peak like that of a gas). This system was developed to enable precise locking of the frequency of a laser used in differential absorption LIDAR measurements of trace atmospheric gases. This system also has great commercial potential as a prototype of means for precise control of frequencies of lasers in future dense wavelength-division-multiplexing optical communications systems.

Posted in: Briefs, Electronics & Computers, Electronic control systems, Lasers, Gases

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Noise Source for Calibrating a Microwave

This compact unit can readily be integrated into an airborne microwave instrumentation. A correlated-noise source has been developed for use in calibrating an airborne or spaceborne Earth-observing correlation microwave polarimeter that operates in a pass band that includes a nominal frequency of 10.7 GHz. Deviations from ideal behavior of the hardware of correlation polarimeters are such as to decorrelate the signals measured by such an instrument. A correlated- noise source provides known input signals, measurements of which can be processed to estimate and correct for the decorrelation effect.

Posted in: Briefs, Electronics & Computers, Calibration, Radar, Noise

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